1. Field of the Invention
The present invention is related to a semiconductor device, and in particular to a semiconductor testing device that measures the electrical field distribution or the voltage distribution or each measured point during testing of a device under test (DUT).
2. Description of Related Art
An example of conventional technology for this type of semiconductor testing apparatus is described in a paper by Shinagawa et al., xe2x80x9cHandy-type high impedance probe using an EOS,xe2x80x9d The 15th Light Wave Technology Research Conference, 1995, pp. 123-129. In addition, the structure of another conventional semiconductor test apparatus is shown in FIG. 7. In this figure, the semiconductor test apparatus has a light source 101, and a pulsed laser is emitted under control of the light source drive circuit 113. The light pulse emitted by the light source 101 is condensed by the condenser lens 102, and condensed onto the electrooptic element 103.
The electrical field generated by the voltage input into and output from each pin of the DUT 105 is also present in the electrooptic element 103. While the light pulse condensed by the condenser lens 102 transits the electrooptic element 103, the polarization thereof changes (modulates) due to the electrical field generated by the measured device 105.
This light pulse is reflected by the reflecting plate 104 provided on the lower surface of the electrooptic element 103, and after transiting the wavelength plate 106 and the analyzer 107, this light is condensed on the electrooptic converter 109 by the condenser lens 108. The analyzer 107 has the property of changing the polarity component of the light to an intensity component, and the signal component of the light polarized by the electrooptic element 103 is converted to an intensity signal (amplitude information) due to transiting the analyzer 107.
The optoelectric converter 109 converts the intensity (amplitude) of the light to the intensity (amplitude) of the electric signal. The electrical field generated by the voltage signal in each of the pins of the measured device 105 is made proportional to the level of the voltage signal, and thereby the amplitude of the electric signal generated in the optoelectric converter 109 is made proportional to the voltage in the measured device 105. This electric signal is amplified by the amplifying circuit 110, and converted to a digital signal by the A/D converting circuit 111.
The trigger signal St is a trigger signal that represents the measurement from the measured device and the like. Based on the A/D conversion timing signal Sc output from the timing generation circuit 114 in synchronicity with this signal, the measurement data of the measured device 105 is input by the A/D conversion circuit 111, A/D converted, and the electrical field and the voltage value are calculated and displayed by the calculation/display circuit 112.
The timing operation of the semiconductor apparatus shown in FIG. 7 is shown in FIG. 8. As shown in this figure, in the case that the light source 101 emits a continuous light, at the timing represented by the AID conversion timing signal Sc, in sequence, the data is input into the A/D conversion circuit 111, A/D converted, and the digital data that has been A/D converted is sent to the calculation/display circuit 112. In this case, the output timing of the trigger signal St serves as the data input commencement timing.
Next, in the case that the light source emits a pulsed light, each time the trigger signal St is input, the pulsed emitted light timing signal Sp from the timing generation circuit 114 is output such that each time the phase is delayed by xcex4t, and the light pulse is emitted from the light source 101 by controlling the drive of the light source drive circuit 113 by the pulsed light emission light timing signal Sp.
In the A/D conversion circuit 111, data is input by the A/D conversion timing output from the timing generating circuit 114, A/D conversion is carried out, and the digital data that has been A/D converted is sent to the calculation/display circuit 112.
In the case that the light source 101 is driven so as to emit pulsed light, the measuring signal of the measured device 105 requires a return signal synchronized with the trigger signal 23. This method is an existing technology called sequential sampling.
In the calculation/display circuit 112, the digital data obtained by the A/D conversion circuit 111 is multiplied by the sensitivity of the measurement system, converted to a voltage or electrical field at the measurement point of the measured device 105, and displayed as a data value, waveform, or a time series.
The conventional technology for the semiconductor test apparatus described above is disclosed in Japanese Patent Application, No. Hei 09-273156. In addition, similar functions for the light source 101, condensing lens 102, the electrooptic element 103, reflecting plate 104, wavelength plate 106, analyzer 107, condenser lens 108, and the optoelectric conversion 109 are disclosed in this publication.
In the above-described EOS (Electro-Optic Sampling)-type semiconductor test apparatus, measurement of only one point on the measured device is possible, and for example, there is the problem that even in the case that the pins of the integrated circuit are arranged in a row, they must be measured by moving the irradiating position of the light beam emitted from the light source for each pin in sequence, and much time must be consumed.
Furthermore, in the case that the distribution of the voltage of electrical field of the entire measured device is measured, there are the problems that the light beam must be swept in two dimensions relative to the measured point, and due to measuring by sweeping the light beam in two dimensions, the system structure becomes complicated, and the measuring time becomes long.
In addition, in the above-described EOS-type semiconductor test apparatus, in the case that a plurality of measured points are to be measured, measurement must be conducted by moving the light beam in sequence, and thus in the case that many points in the measured device are measured simultaneously (at the same time), there is the problem that a plurality of sensors is necessary.
In light of the above-described circumstances, it is an object of the present invention to provide a semiconductor test apparatus that can measure the voltage distribution and the electrical field distribution of the measured device in one or two dimensions, and can implement a reduction in the measuring time.
In order to attain the above objectives, in a semiconductor test apparatus wherein a light beam emitted from a light source irradiates a measured part of a measured device via an electrooptic element arranged above the measured device and the electrical field distribution or the voltage distribution in the measured part of the measured device is calculated by electrically detecting the change in the state of the polarization of this reflected beam, a first aspect of the invention is characterized in comprising a first optical system wherein light emitted from the light source is shaped into a line-shaped light beam and irradiates a desired measurement line on the measured device via the electrooptic element, a second optical system that maintains as-is the shape of the line-shaped light beam reflected from the desired measurement line on the measured device after transiting the electrooptic element, and modulates the change in polarity of the line-shaped light beam to a change in intensity of the light, a light receiving device that receives the line-shaped light beam emitted from the second optical system and converts the light beam at each of the measured points to an electrical signal depending on the strength of each light beam reflected at each of the measured points on the desired measurement line on the measured device and outputs the result, and a signal processing device that calculates the voltage or electrical field at each of the measured points of the measured device from the output signal of the light receiving device and calculates the electrical field distribution or the voltage distribution at the measured part of measured device.
In addition, in a second aspect of the invention, in the semiconductor test apparatus according to the first aspect, the signal processing device is characterized in comprising a sample holding circuit that holds samples of the output signal of the light receiving device simultaneously for each of the measured points of the measured device, a selection circuit that selects in sequence the samples of the signals held by the sample holding circuit, an A/D conversion circuit that A/D converts the analog signal selected by the selecting circuit, and a timing generation circuit that outputs a timing signal that controls the operating timing of the sample holding circuit, the selection circuit, and the A/D conversion circuit.
In addition, in a third aspect of the invention, in the semiconductor test apparatus according to the first aspect, the first optical system comprises a condenser lens that condenses the light emitted from the light source, and a curved mirror that shapes the light beam condensed by the condenser lens into a line-shaped light beam and irradiates a desired measurement line on the measured device via an electrooptic element.
In addition, in a fourth aspect of the invention, in the semiconductor test apparatus according to the first aspect, the second optical system comprises a reflecting plate that is arranged on the lower surface of the electrooptic element, and reflects the line-shaped light beam irradiated by the first optical system, a wavelength plate that converts the line-shaped light beam reflected by the reflecting plate to line-shaped polarized light, an analyzer that converts an amount of polarization of the line-shaped light beam that has transited the wavelength plate to an amount of amplitude, and a microlens array that condenses each of the reflected light beams corresponding to each of the measured points of the measured device on the line-shaped light beam that has transited the analyzer on each of the light receiving surfaces of the light receiving device corresponding to each of the reflected light beams.
In addition, in a fifth aspect of the invention, in the semiconductor test apparatus according to the first aspect, the semiconductor test apparatus further comprises a calculation/display device, and this calculation/display device calculates and displays the electrical field or the voltage value based on the output signals of the A/D converting circuit.
In addition, in a sixth aspect of the invention, in the semiconductor test apparatus according to any of the first through fifth aspects, the calculation/display device displays the electrical distribution or the voltage distribution on the measurement line of the measured device that has been obtained based on the amplitude information of the reflected beam of the line-shaped light beam irradiating the measured device via the electrooptic element.
In addition, in a seventh aspect of the invention, in a semiconductor test apparatus according to the fifth aspect, the signal processing means calculates a plurality of times the electrical field distribution or voltage distribution on the measurement line of the measured device obtained based on the amplitude information of the reflected beam of the desired line-shaped light beam that irradiates the measured part of the measured device, and the calculation/display device displays on a time axis the electrical field distribution or voltage distribution on the measurement line of the measured device that have been calculated a plurality of times.
In addition, in an eighth aspect of the invention, in a semiconductor test apparatus according to the first aspect, the light source is driven so as to emit light continuously, and at each timing wherein the A/D conversion of the signal representing the electrical field or voltage at each of the measured points of the measured part in the measured device irradiated by the line-shaped light beam has completed, the sample holding circuit holds samples of the signals representing the electrical field or voltage at each of the measured points.
In addition, in a ninth aspect of the invention, in a semiconductor test apparatus according to the first aspect, the timing is such the A/D conversion rate of the A/D converting device ADDed to the number of signals output from the light receiving device becomes equal to the sample rate of the sample holding circuit, and the light source is driven so as to emit pulsed light at a timing synchronous with a reference signal that determines the measurement timing, and at the same time, the sample holding circuit holds samples of the signals that represent the electrical field or the voltage of each of the measured points at the measured parts of the measured device irradiated by the line-shaped light beam at a timing in synchronism with the light emission timing.
In addition, in a tenth aspect of the invention, in a semiconductor test circuit according to the first aspect, the signal processing means is characterized in comprising a plurality of amplifying circuits that amplify each of the plurality of output signals output from the light receiving devices, a plurality of A/D conversion circuits that A/D convert each of the output signals of the plurality of amplifying circuits, a plurality of latch circuits that latch the output signals of the plurality of A/D conversion circuits, and a selection circuit that selects in sequence each of the outputs of the plurality of latch circuits.
In addition, in an eleventh aspect of the present invention, in the semiconductor test circuit according to the first aspect, the magnetic field distribution or the current distribution in the desired measured part of the measured device are calculated using a magneto-optic element instead of the electrooptic element.
According to the first aspect of the invention, in a semiconductor test apparatus wherein a light beam emitted from a light source irradiates a measured part of a measured device via an electrooptic element arranged above the measured device and the electrical field distribution or the voltage distribution in the measured part of the measured device is calculated by electrically detecting the change in the state of the polarization of this reflected beam, a first aspect of the invention is characterized in comprising a first optical system wherein light emitted from the light source is shaped into a line-shaped light beam and irradiates a desired measurement line in the measured device via the electrooptic element, a second optical system that maintains as-is the shape of the line-shaped light beam reflected from the desired measurement line in the measured device after transiting the electrooptic element, a light receiving device that receives the line-shaped light beam emitted from the second optical system and converts and outputs for each of the measured points to an electrical signal depending on the strength of each light beam reflected at each of the measured points on the desired measurement line on the measured device, and a signal processing device that calculates the voltage or electrical field at each of the measured points of the measured device from the output signal of the light receiving device and calculates the electrical field distribution or the voltage distribution at the measured part of measured device, and thereby the one-dimensional or two-dimensional voltage distribution or electrical field distribution in a measured device can be calculated, and a reduction of the calculating time can be implemented.
In addition, according to the eleventh aspect of the invention, in the semiconductor test circuit according to the first aspect, the magnetic field distribution and the current distribution in the desired measured part of the measured device are calculated using a magneto-optic element instead of the electrooptic element, and thereby voltage distribution or electrical field distribution in a measured device can be calculated in one-dimension or two-dimensions, and thereby a reduction of the calculating time can be implemented.